Keywords:

Electron measurement;

Geomagnetic tail;

Magnetic reconnection;

Magnetopause;

Three-dimensional MHD modeling

Summary

The event of March 22, 1979 has been the object of a concentrated study effort as a part of the Coordinated Data Analysis Workshop activity designated CDAW-6. Energetic electron and magnetic field measurements from a set of four satellites aligned from 6.6 to 13 RE at the 0200 LT meridian at the time of the magnetospheric substorm event of 1100 UT are presented. These data are used to show that a magnetic X-line formed spontaneously in the region of 7 to 10 RE in response to a steady build-up of magnetic stress in the geomagnetic tail.